Imaging a plurality of images using a plurality of non-parallel scan paths

ABSTRACT

Methods are provided for imaging patterns on a media. The steps of the method include operating a first imaging head with individually addressable channels to direct imaging beams to form a first image on the media while scanning over the media along a scan path. A second imaging head with individually addressable channels is operated, either at the same time or a different time, to direct imaging beams to form a second image on the media while scanning over the media along a second scan path. It is possible that the first scan path may or may not be parallel to the second scan path, and that the first image may or may not be aligned with the second image. The first image may or may not be skewed with respect to the second image.

This is a U.S. National Stage application under 35 U.S.C. 371 ofInternational Application No. PCT/IB2007/001089, filed Apr. 26, 2007.

TECHNICAL FIELD

The invention relates to imaging systems and to methods for imaging aplurality of patterns disposed on the same media. The invention may beapplied to fabricating color filters for electronic displays, forexample.

BACKGROUND

Color filters used in display panels typically include a matrixcomprising a plurality of color features. The color features may includepatterns of red, green and/or blue color features, for example. Colorfilters may be made with color features of other colors. The colorfeatures may be arranged in any of various suitable configurations.Prior art stripe configurations have alternating columns of red, greenand blue color features as shown in FIG. 1A.

FIG. 1A shows a portion of a prior art “stripe configuration” colorfilter 10 having a plurality of red, green and blue color features 12,14 and 16 respectively formed in alternating columns across a media orreceiver element 18. Color features 12, 14 and 16 are outlined byportions of a matrix 20. The columns can be imaged in elongate stripesthat are subdivided by matrix cells 34 (herein referred to as cells 34)into individual color features 12, 14 and 16. TFT transistors on theassociated LCD panel (not shown) may be masked by areas 22 of matrix 20.

Laser-induced thermal transfer processes have been proposed for use inthe fabrication of displays, and in particular color filters. Whenlaser-induced thermal transfer processes are used to produce a colorfilter, a color filter substrate also known as a receiver element isoverlaid with a donor element that is then image-wise exposed toselectively transfer a colorant from the donor element to the receiverelement. Preferred exposure methods use radiation beams such as laserbeams to induce the transfer of the colorant to the receiver element.Diode lasers are particularly preferred for their ease of modulation,low cost and small size.

Laser induced “thermal transfer” processes include: laser induced “dyetransfer” processes, laser-induced “melt transfer” processes,laser-induced “ablation transfer” processes, and laser-induced “masstransfer” processes. Colorants transferred during laser-induced thermaltransfer processes include suitable dye-based or pigment-basedcompositions. Additional elements such as one or more binders may betransferred, as is known in the art.

Some conventional laser imaging systems have employed a limited numberof imaging beams. Other conventional systems have employed hundreds ofindividually-modulated beams in parallel to reduce the time taken tocomplete images. Imaging heads with large numbers of such “channels” arereadily available. For example, a SQUAREspot® model thermal imaging headmanufactured by Kodak Graphic Communications Canada Company, BritishColumbia, Canada has several hundred independent channels. Each channelcan have power in excess of 25 mW. The array of imaging channels can becontrolled to write an image in a series of image swaths which areclosely abutted to form a continuous image.

The stripe configuration shown if FIG. 1A illustrates one exampleconfiguration of color filter features. Color filters may have otherconfigurations. Mosaic configurations have the color features thatalternate in both directions (e.g. along columns and rows) such thateach color feature resembles an “island”. Delta configurations(not-shown) have groups of red, green and blue color features arrangedin a triangular relationship to each other. Mosaic and deltaconfigurations are examples of “island” configurations. FIG. 1B shows aportion of a prior art color filter 10 arranged in a mosaicconfiguration in which color features 12, 14 and 16 are arranged incolumns and alternate both across and along the columns. Other colorfilter configurations are also known in the art.

Each of color features 12, 14 and 16 may overlap adjoining portions ofmatrix 20. Overlapping matrix 20 with the color features can reduceleakage of backlight between the features. FIG. 1C schematically shows aconventional stripe configuration color filer in which the colorfeatures 12, 14 and 16 are formed from color stripes that fully overlapportions of matrix 20 along columns of the filter but partially overlapmatrix 20 along the rows of the filter. FIG. 1D schematically shows aconventional mosaic configuration color filter in which each of thecolor features 12, 14 and 16 are islands that each partially overlapmatrix 20 across both the rows and columns of the filter. Inapplications like color filters, the visual quality of the final productis dependant upon how accurately a repeating pattern of features (e.g.the pattern of color filter features) is registered with a repeatingpattern of registration sub-regions (e.g. matrix). Misregistration canlead to the formation of undesired colorless voids and/or theoverlapping of adjacent color features which can form an undesired colorcombination.

Overlapping a matrix may help to reduce the precision with which thecolor features must be registered with matrix. However, there typicallyare limits to the extent that a matrix can be overlapped. Factors thatcan limit the degree of overlap (and final registration) can include,but are not limited to: the particular configuration of the colorfilter, the width of the matrix lines, the roughness of the of thematrix lines, the minimum overlap required to prevent light backleakage, and post annealing color features shrinkage.

Factors associated with the particular method employed to produce thefeatures can limit the degree of overlap. For example, when laserimaging methods are employed, the precision with which the laser imagercan scan the color filter will be applicable to the final registrationobtained. The addressability associated with the imaging channels of theimaging head defines the resolution with which the features can beimaged also has a bearing on the final registration. The orientation ofthe color filter with respect to a scan path of the imaging head canalso have a bearing on the registration.

The laser imaging process employed can also have an effect on the degreeof overlap that is permitted. For example, the visual quality of animage produced in a laser-induced thermal transfer process is typicallysensitive to the amount of image forming material that is transferredfrom a donor element to a receiver element. The amount of transferredimage forming material is typically sensitive to the spacing between thedonor element and receiver element. If adjacent features of differentcolors overlap themselves over portions of the matrix, thedonor-to-receiver element spacing will additionally vary during thesubsequent imaging of additional donors elements, possibly impacting thevisual quality of the features imaged with these additional donorelements. In this regard, it is preferred that adjacent features ofdifferent colors not overlap themselves over a matrix portion. Thisrequirement places additional registration constraints on the requiredregistration between the pattern of repeating color features and therepeating pattern of matrix cells.

To increase production throughput, a plurality of color filter displaysis usually formed on a universal receiver element 18 and which issubsequently imaged with different color donor elements usinglaser-induced thermal transfer techniques to image the plurality ofdisplays. Post-imaging, the universal receiver element 18 is separatedto form the individual color filter displays. Although a matrix 20 canbe produced on a receiver element 18 by laser-induced thermal transfertechniques, matrix 20 is typically produced by standardphotolithographic methods. Photolithographic techniques typically employan exposure apparatus to illuminate a mask to form a pattern on asubstrate. Upon exposure the pattern is developed and a medium istransferred to the substrate via the pattern to form various entitiessuch as matrix 20.

However, photolithographic techniques can become expensive when largeuniversal substrates are exposed since both larger exposure units andmasks are needed. To help mitigate these additional costs, smaller masksare employed with step and repeat exposure apparatus. A plurality ofsmaller masks are superposed over the substrate and imaged in a step andrepeat fashion with smaller exposure units. Although these techniquesmay reduce the costs of forming multiple matrixes on a single universalsubstrate, additional problems may arise during the subsequent formationof the color features. For instance, the use of a plurality of masks maylead to varying degrees of misregistration between the multiple backmatrixes that are formed. Misregistration between multiple matrixescreate additional challenges in terms of accurately imaging a pluralityof repeating color feature patterns in correct registration with theircorresponding matrixes disposed on a universal receiver element.

There remains a need for effective and practical imaging methods andsystems that permit the making of a plurality of high-quality images ofrepeating patterns of features, such as the patterns of color featuresin a color filter on a universal substrate.

There remains a need for imaging methods and systems that permit themaking of a repeating patterns of features (e.g. the patterns of colorfeatures in a color filter), in register with a repeating pattern ofregistration sub-regions (e.g. the pattern of cells in a matrix).

SUMMARY OF THE INVENTION

The present invention includes a method for forming a plurality ofimages on a receiver element, such as, for example, a substratecontaining a matrix for a color filter. A computer program may becreated to cause a controller to carry out the steps of the method.

The images created may include a repeating pattern of features ofvarious possible shapes, color combinations, configurations and spacing.For example, the repeating pattern of features may be a continuous ordiscontinuous stripe. The images may be a repeating pattern of islandfeatures, which can include a pattern of features of one color separatedfrom one another by a pattern of features of a different color in one ormore directions.

The process may include transferring an image forming material from adonor element to the receiver element. The images may be formed througha laser-induced thermal transfer process, such as a laser-induced dyetransfer process, laser-induced mass transfer process, or bytransferring a colorant and a binder to the receiver element. In oneembodiment, each feature of the pattern may be screened with a half tonescreen or a stochastic screen. If the receiver element includes amatrix, the matrix may be made by a process different from laser-inducedthermal transfer.

The method includes operating a first imaging head with individuallyaddressable channels to direct imaging beams to form a first image onthe receiver element while scanning over the receiver element along ascan path. A second imaging head with individually addressable channelsis operated, either at the same time or a different time, to directimaging beams to form a second image on the receiver element whilescanning over the receiver along a second scan path. It is possible thatthe first scan path may not be parallel to the second scan path, andthat the first image may not be aligned with the second image. The firstimage may or may not be skewed with respect to the second image.

The imaging heads and receiver element are moved relative to oneanother, by either moving the imaging heads, or the receiver, or both.The relative speeds of the first and second imaging heads may be thesame or may be different from one another. The channels are controlledby activation timing, which determines when the individual channelsimage. Because the channels of each imaging head are individuallyaddressable, one, or a portion, may activated while others are not atany given time, while relative movement of the heads and receiverelement occurs.

The first imaging head may direct imaging beams to form a third image onthe receiver element while scanning along a third scan path. The thirdimage may or may not be aligned, skewed and/or parallel with the firstimage.

The receiver element may include one or more registration regions. It ispreferable to align the scan path to image a portion of an image insubstantial registration with a registration region, which may be doneby causing relative motion along both a main scan direction and asub-scan direction. Adjustments to activation timing of a portion of theindividually addressable channels or modification of the image data, by,for example, shearing the data, can also be used to create the image insubstantial registration with a registration region.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments and applications of the invention are illustrated by theattached non-limiting drawings. The attached drawings are for purposesof illustrating the concepts of the invention and may not be to scale.

FIG. 1A is a plan view of a portion of a prior art color filter;

FIG. 1B is a plan view of a portion of another prior art color filter;

FIG. 1C is a plan view of an orientation of color features with a matrixof a prior art color filter;

FIG. 1D is a plan view of an orientation of color features with a matrixof another prior art color filter;

FIG. 2 is a schematic view of a multi-channel head imaging a pattern offeatures onto an imageable media;

FIG. 3 is a partially schematic perspective view of the optical systemof an example prior art multi-channel imaging head;

FIG. 4 is a schematic view of an apparatus used in an example embodimentof the invention;

FIG. 5 is a flow chart for an imaging method of an example embodiment ofthe invention;

FIG. 6 is schematic cross-sectional view of the apparatus of FIG. 4;

FIG. 7 is a beam finder used in an example embodiment of the invention;

FIG. 8 is schematic representation of an intensity profile created bydirecting radiation beams on the beam finder of FIG. 7;

FIG. 9A is a schematic representation of a receiver element;

FIG. 9B is a schematic representation of a conventional imaging of thereceiver element of FIG. 9A;

FIG. 9C is a schematic representation of a step used to form an image onthe receiver element of FIG. 9A as per an example embodiment of theinvention;

FIG. 9D is a schematic representation of a step used to form an image onthe receiver element of FIG. 9A as per an example embodiment of theinvention;

FIG. 9E is a schematic representation of a step used to form an image onthe receiver element of FIG. 9A as per an example embodiment of theinvention;

FIG. 10A is a representation of an orientation between two colorfeatures and a matrix portion;

FIG. 10B is a schematic view of an imaging of a pattern of the colorfeatures of FIG. 10A;

FIG. 10C is representation of a possible registration affect of severalcolor features of FIG. 10B;

FIG. 10D is representation of a possible registration affect of severalcolor features of FIG. 10B;

FIG. 10E is a schematic view of an imaging of a pattern of the colorfeatures of FIG. 10A as per an example embodiment of the invention;

FIG. 11A is an example representation of a desired registration of arepeating pattern of features with a registration region;

FIG. 11B is schematic view of a conventional imaging of the pattern offeatures of FIG. 11A.

FIG. 11C is a schematic view of an imaging of the pattern of features ofFIG. 11A as per an example embodiment of the invention;

FIG. 12 is a schematic view of a skewed imaging of the pattern offeatures of FIG. 11A as per an example embodiment of the invention,

FIG. 13 is a schematic view of an imaging of the pattern of features ofFIG. 11A as per an example embodiment of the invention that employs azoom mechanism; and

FIG. 14 is schematic representation of a zoom mechanism as per anexample embodiment of the invention.

DETAILED DESCRIPTION

Throughout the following description specific details are presented toprovide a more thorough understanding to persons skilled in the art.However, well-known elements may not have been shown or described indetail to avoid unnecessarily obscuring the disclosure. Accordingly, thedescription and drawings are to be regarded in an illustrative, ratherthan a restrictive, sense.

FIG. 2 schematically shows a portion of a color filter receiver element18 that has been conventionally patterned with a repeating featurepattern 30 of stripe features 32 (red in this example) in alaser-induced thermal transfer process. In this process, areascorresponding to the stripe features 32 are imaged on receiver element18 by the transfer of the image-forming material (not shown) from donorelement 24 onto receiver element 18. In FIG. 2 donor element 24 is shownas being smaller than receiver element 18 for the purposes of clarityonly. Donor element 24 may overlap one or more portions of receiverelement 18 as may be required.

For the sake of clarity, only red stripe features 32 are shown in FIG.2. Different colored portions of filter 10 are typically imaged inseparate imaging steps, each imaging step using a different color donorelement appropriate for the color to be imaged. Each donor element 24 isremoved upon completion of the corresponding imaging step. After thecolor features have been transferred, the imaged color filter may besubjected to one or more additional process steps, such as an annealingstep for example, to change one or more physical properties (e.g.hardness) of the imaged color features.

The areas of receiver element 18 onto which the stripe features 32 arepatterned are not chosen randomly. Rather, stripe features 32 are formedin substantial register with a registration region 35 (shown in brokenlines) associated with receiver element 18. In this example,registration region 35 includes matrix 20 which is formed on receiverelement 18. Matrix 20 includes a plurality of cells 34 which arearranged into a repeating registration pattern 36 of the cells. In thisexample, feature pattern 30 is “ideally” registered with registrationpattern 36 with portions of stripe features 32 completely overlapportions of matrix 20 along a direction aligned with main-scan axis 42and partially overlap other portions of matrix 20 along a directionaligned with sub-scan direction 44. The allowable amount of partialoverlap in part defines the degree of registration between featurepattern 30 and registration pattern 36.

Image-forming material is image-wise transferred onto the receiverelement 18 when imaging beams (not shown) emitted by imaging head 26 arescanned across donor element 24. Imaging head 26 includes an array ofindividually addressable imaging channels 40. The imaging beamsgenerated by imaging head 26 are scanned over receiver element 18 in amain-scan direction 42 while being image-wise modulated according toimage data specifying the pattern of features to be written. Groups 48of channels are driven appropriately to produce imaging beams withactive intensity levels wherever it is desired to form a feature.Channels 40 not corresponding to the features are driven so as not toimage corresponding areas.

An example of an illumination system employed by a conventionallaser-based multi-channel imaging head is schematically shown in FIG. 3.A spatial light modulator or light valve is used to create a pluralityof imaging channels. In the illustrated example, linear light valvearray 100 includes a plurality of deformable mirror elements 101fabricated on a semi-conductor substrate 102. Mirror elements 101 areindividually addressable. Mirror elements 101 can bemicro-electro-mechanical (MEMS) elements, such as deformable mirrormicro-elements, for example. A laser 104 can generate an illuminationline 106 on light valve 100 using an anamorphic beam expander comprisingcylindrical lenses 108 and 110. Illumination line 106 is laterallyspread across the plurality of elements 101 so that each of the mirrorelements 101 is illuminated by a portion of illumination line 106. U.S.Pat. No. 5,517,359 to Gelbart describes a method for forming anillumination line.

A lens 112 typically focuses laser illumination through an aperture 114in an aperture stop 116 when elements 101 are in their un-actuatedstate. Light from actuated elements is blocked by aperture stop 116. Alens 118 images light valve 100 to form a plurality of individualimage-wise modulated beams 120, which can be scanned over the area of asubstrate to form an image swath. Each of the beams 120 is controlled byone of the elements 101. Each element 101 controls a channel of amulti-channel imaging head

Each of the beams is operable for imaging, or not imaging, an “imagepixel” on the imaged substrate in accordance with the driven state ofthe corresponding element 101. That is, when required to image a pixelin accordance with the image data, a given element 101 is driven toproduce a corresponding beam with an active intensity level suitable forimparting a pixel image on the substrate. When required not to image apixel in accordance with the image data, a given element 101 is drivento not produce an imaging beam. An imaging beam emitted by an imaginghead channel can travel various paths to form a corresponding pixel. Animaging beam can be deflected along a path. As used herein, pixel refersto a single element of image on the substrate, as distinguished from theusage of the word pixel in connection with a portion of an imagedisplayed on an assembled display device. For example, if the presentinvention is used to create a filter for a color display, the pixelscreated by the present invention will be combined with adjacent pixels,to form a single pixel of an image displayed on the display device.

Referring back to FIG. 2, receiver element 18, imaging head 26, or acombination of both are displaced relative to one another while thechannels 40 of the imaging head 26 are controlled in response to imagedata to create imaged swaths. In some cases the image of imaging head 26is stationary and receiver element 18 is moved. In other cases, receiverelement 18 is stationary and imaging head 26 is moved.

Channels 40 of imaging head 26 can image a swath having a width relatedto the distance between a first pixel imaged by a first channel 46 and alast pixel imaged by a last channel 45. Receiver element 18 is typicallytoo large to be imaged within a single swath. Therefore, multiple scansof each imaging head 26 are typically required to complete variousimages on receiver element 18.

Movement of imaging head 26 along sub-scan direction 44 may occur afterthe imaging of each swath is completed in main-scan direction 42.Alternatively, imaging head 26 may be translated relative to receiverelement 18 along sub-scan direction 44 in synchrony. With a drum-typeimager, it may be possible to simultaneously move imaging head 26 inboth the main-scan direction 42 and sub-scan directions 44, thus writingthe image in swath extending helically on the drum. Those skilled in theart will appreciate that there are other possible patterns of relativemovement between imaging head 26 and receiver element 18 that could beused to image the desired imaging area on receiver element 18.

Any suitable mechanism may be applied to move imaging head 26 over areceiver element 18. Flat bed imagers are typically used for imagingreceiver elements 18 that are relatively rigid, as is common infabricating display panels. A flat bed imager has a support that securesa receiver element 18 in a flat orientation. U.S. Pat. No. 6,957,773 toGelbart describes a high-speed flatbed imager suitable for display panelimaging. Alternatively, flexible receiver elements 18 may be secured toeither an external or internal surface of a “drum-type” support toaffect the imaging of the swaths. Even a receiver element that istraditionally thought of as rigid, such as glass, may be imaged on adrum-based imager provided that the substrate is sufficiently thin andthe diameter of the support is sufficiently large.

FIG. 2 depicts an “idealized” correspondence between imaging channelgroups 48 and the transferred pattern as broken lines 41. Features, suchas stripe features 32 generally have dimensions in sub-scan direction 44that are greater than the widths of pixels imaged by imaging channels40. Such features may be imaged by turning on a group of channels thatspans the width of the feature in sub-scan direction 44 while scanningthe channels along a scan path. The correspondence between the channelsgroups 48 and stripe features 32 is idealized since in this example,channels 40 in channel groups 48 would need to form pixels of an idealsize that would lead to the formation of stripe features 32 with thecorrect size and periodicity to be correctly registered with matrix 20.The example shown in FIG. 2 is also idealized since the formation ofimage feature pattern 30 occurs while relative motion exists betweenhead 26 and receiver element 18 along a scan path that is parallel tocells 34, thus facilitating the substantial registration of featurepattern 30 with matrix 20.

Ideal imaging conditions are not present however in many circumstances.Different articles of manufacture can have different registrationpatterns and different cell sizes. For example, the matrixes employed incomputer applications typically have different cell sizes andperiodicities than the matrixes employed in television applications.Such variances can make it difficult to address these different productconfigurations with a universal imaging system. Misorientation ofregistration patterns with the scan paths of the multi-channel imagingheads can also increase the difficulties associated with the accuratelyregistering a repeating pattern of features with the repeatingregistration patterns. As further production throughput demands requirethat a plurality of multi-channel imaging heads be employed, additionalburdens for the registrations requirements are additionally created.

FIG. 4 schematically shows an apparatus 50 used in an example embodimentof the invention. Apparatus 50 is operable for forming images onreceiver element 18A. Receiver element 18A includes a plurality ofregistration regions 47A, 47B, 47C and 47D, which are collectivelyreferred to as registration regions 47 and are shown in broken lines. Inthis example embodiment of the invention each registration region 47includes a matrix 20. Each matrix 20 includes a plurality of cells 34.Cells 34 can be rectangular in shape as shown in FIG. 1A or any othersuitable shape required by a given color filter configuration. In thisexample embodiment, matrixes 20 also can include various registrationmarks. In this example, registrations marks 21A, 21B and 21C(collectively known as registration marks 21) are associated with eachregistration region 47. Registration marks 21 can include but are notlimited to various registration indicia or fiducials. Registration marks21 can include various graphical shapes suitable for registrationpurposes (e.g. crosses) and can be formed from the same materials and/orprocess that is employed to produce the matrixes 20 themselves. As shownin FIG. 4, three registration features 21 are associated with eachmatrix 20. In this example embodiment of the invention, eachregistration region 47 includes a plurality of registration marks 21that can be used to define an orientation of the registration regionwith respect to receiver element 18A. In this example embodiment of theinvention, several of the registration regions 47 have differentorientations with respect to other registration regions 47.

When producing multiple numbers of color filters on one or more receiverelements, misalignment of the matrixes 20 with respect to one anothercan occur as shown in FIG. 4. Translational and rotational (i.e. skew)misalignment can arise between the various matrixes. Misalignmentbetween the various matrixes 20 can arise during the formation of thematrixes especially when step and repeat photolithographic techniquesare employed. As shown in FIG. 4, registration region 47A is oriented atangle θ₁ which differs from angle θ₂ that registration region 47B isoriented to. Registration regions 47C and 47D are respectively laterallydisplaced from registration regions 47A and 47B by distance Δ₁ and Δ₂(Δ₁ differing from Δ₂). The magnitudes of angles θ₁, θ₂, anddisplacements Δ₁ and Δ₂ are emphasized for the sake of clarity. Invarious example embodiments of the invention, the magnitudes may besmaller. For instance, in color filter application, misalignment betweena plurality of matrixes formed on a receiver element can typically bemeasured in micro-radians and microns. Nonetheless, even such smallmisalignments between various registration regions can hamper efforts toaccurately register a repeating pattern of features with a repeatingpattern of registration sub-regions defined within the registrationregions.

In this example embodiment of the invention, images are formed onreceiver element 18A by a laser-induced thermal transfer process.Receiver element 18A is positioned on carrier 51 which includes atemplate 52 that allows receiver element 18A to be approximately alignedand positioned within a predetermined area of carrier 51. Template 52 isslightly larger than receiver element 18A in size. Carrier 51 isoperable for conveying receiver element 18A along path aligned withmain-scan direction 42. A plurality of multi-channel imaging heads 26Aand 26B (collectively known as imaging heads 26) are arranged on asupport 53. Each imaging head 26 is controlled to move independently ofthe other imaging head 26 along paths aligned with sub-scan direction44. In this example embodiment of the invention, sub-scan direction 44is substantially perpendicular to main-scan direction 42. In thisexample embodiment of the invention, each of the imaging heads 26includes one or more vision systems 56 that move along paths alignedwith sub-scan direction 44 in accordance with their respective imagingheads 26. In this example embodiment vision system 56 includes a CCDcamera 57, and flash 58. CCD camera 57 can include a CCD and associatedoptical elements to capture suitable images of receiver element 18A. Inthis example embodiment of the invention, the optical elements include amicroscope 61. In this example embodiment of the invention, a donorelement 24 (not shown in FIG. 4) is appropriately positioned on receiverelement 18 and carrier 51 conveys the media assemblage along a pathaligned with main-scan directions 42. During this motion, imaging heads26 are controlled to scan the media assemblage with a plurality ofradiation beams to cause a transferal of an image forming material (notshown) from donor element 24 to receiver element 18A to form images onreceiver element 18A. Imaging electronics 84 control the activation ofthe imaging channels of each imaging head 26 to regulate the emission ofthe radiation beams. In this example embodiment of the invention, eachregistration region 47 is imaged by a single imaging head 26, althoughit is understood that each registration region 47 can be imaged by aplurality of imaging heads and therefore any suitable number of imagingheads can be used in other embodiments of the invention.

Motion system 59 which can include one or more motion systems thatinclude any suitable prime movers, transmission members, and/or guidemembers causes the motion of carrier 51. In this example embodiment ofthe invention motion system 59 also controls the independent motion ofeach of imaging heads 26A and 26B along corresponding paths aligned withsub-scan direction 44. Those skilled in the art will readily realizethat separate motion systems can also be used to operate differentsystems within apparatus 50.

Controller 60, which can include one or more controllers is used tocontrol one or more systems of apparatus 50 including but not limited tovarious motion systems 59 used by carrier 48 and imaging heads 26.Controller 60 can also control media handling mechanisms that caninitiate the loading and for unloading of receiver elements 18A anddonor elements 24. Controller 60 can also transfer image forming data tothe imaging heads 26 and control the imaging heads to emit imaging beamsin accordance with this data. Controller 60 can also be used to controlvision systems 56. These various systems can be controlled using variouscontrol signals and/or implementing various methods. Controller 60 maybe configured to execute suitable software and may comprise one or moredata processors, together with suitable hardware, including by way ofnon-limiting example: accessible memory, logic circuitry, drivers,amplifiers, A/D and D/A converters, input/output ports and the like.Controller 60 may comprise, without limitation, a microprocessor, acomputer-on-a-chip, the CPU of a computer or any other suitablemicrocontroller. Controller 60 associated with the exposure systemsdescribed above may be, but need not necessarily be, the samecontrollers that control the operation of the corresponding materialshandling systems.

Apparatus 50 forms images in each of the registration regions 47. Inthis example embodiment of the invention, apparatus 50 forms variouscolor filter feature patterns (not shown). The visual quality of each ofeach of the color filter feature patterns alone or combined is dependantupon the ultimate registration between the formed images and theregistration regions 47. In this example embodiment of the invention,the visual quality of each of the color filters is dependant upon theregistration of the imaged color features with the matrix 20 of thecorresponding color filter.

Many factors can affect imaging registration. For example, if a receiverelement is made from glass, a temperature increase of 1 deg. Celsius canresult in approximately 10 microns or more of expansion in receiverelement. A typical matrix line width can be 20 microns or less, and sucha degree of thermal mis-registration could lead to the presence ofcolorless voids or overlapping color elements, of which both effectsdiminish the quality of the final color filter.

The position of receiver element 18A with respect to template 52 canaffect imaging registration. Although automation (e.g. robotic loaders)can be used to load a receiver element 18 within the confines oftemplate 52, some degree of registration errors are very likely tooccur. Misregistration of receiver element 18A with template 52 caninclude translational misregistration as well as rotationalmisregistration.

Before apparatus 50 can image each of the registration regions 47, theorientation of each of the registration regions 47 must be determined asreferenced with the imaging directions (i.e. main-scan direction 42 andsub-scan direction 44). In this example embodiment of the invention,vision systems 56 are used to accurately locate registration regions 47.

FIG. 5 shows a flow chart for determining the location of theregistration regions 47 and forming images in the aligned relationshipwith registration regions 47 as per an example embodiment of theinvention. It will be understood that the steps in FIG. 5 do not have tobe performed in the order shown. For example, the pitch and substraterotation correction can be performed before preparing the imagingapparatus for imaging. The FIG. 5 flow chart refers to apparatus 50 asschematically shown in FIG. 4, although it is understood that otherapparatus are suitable for use with the illustrated process. The processbegins at step 300 when registration region information 62 is providedto controller 60 to identify the location of each registration region47. Registration region information 62 can include, but is not limitedto the number of registration regions 47 present on the receiver element18A, the number and type of registration marks 21 associated with eachof the registration regions, the position of the registration marks 21within their respective regions, the spacing between each of therespective registration regions, and any relevant matrix 20 information(e.g. the pitch spacing between matrix cells). Registration regioninformation 62 can be provided in any suitable data entry form tocontroller 60.

In step 320, the actual position of each registration region 47 isdetermined. In this example embodiment of the invention, a hunt for eachof the registration marks 21 associated with each of the registrationregions 47 is made. Controller 60 provides signals to the motion systems59 and vision systems 56 in accordance with the registration regioninformation 62 to initiate this hunt. Controller 60 can receive feedback signals from motion systems 59 and vision systems 56.

In this example embodiment of the invention, flashes 58 and CCD cameras57 are synchronized with motion systems 59. For example, when motionsystem 59 positions receiver element 18A under a given microscope 61, anassociated flash 58 is triggered to generate an illuminating flash oflight for a specific distance as CCD camera 57 captures an image duringthe positioning. As speed of the motion system increases, a brighterflash of light is triggered. In this example embodiment of theinvention, imaging heads 26 and their associated vision systems 56 arepositioned at various locations aligned with sub-scan directions 44. Asmotion systems 59 moves receiver element 18A along a paths aligned withmain-scan direction 42 each vision system 50 capture as series ofmultiple images at specific determined points on receiver element 18A.This process is referred to as “dynamic capture”.

Typically, since the field of view of each microscope 61 is small,apparatus 50 must perform a multi-image hunt for the registration marks21 that define each registration region 47. A minimum of threenon-colinear registration marks 21 are needed to define a position ofeach registration region 47 in a reference frame related to main-scandirections 42 and sub-scan directions 44. Geometric location software(e.g. Adept Hexsight, distributed by Adept Technologies, Inc. ofLivermore, Calif.) is used to determine if, and where a registrationmark 21 appears in each captured image. Inputs to this softwaretypically include what each registration mark 21 looks like as well asthe captured image coordinates.

In accordance with registration region information 62, controller 60enables motion systems 59 to independently position each of the imagingheads 26 at various preliminary positions aligned with sub-scandirection 44. As shown in FIG. 4, imaging head 26A has been moved to apreliminary position with respect to registration regions 47A and 47C.Imaging head 26B has been moved to a preliminary position with respectto registration regions 47B and 47D. The hunt is expedited by firstlocating two of the three registration marks of each registration region47. For example, registration marks 21A and 21B associated with each ofregistration regions 47A and 47C are located in a square search hunt inwhich imaging head 26A is moved to a first sub-scan position where itsassociated vision system 50 dynamically captures a column of images asreceiver element 18A is moved along a path aligned with main-scandirection 42. Geometric location software is used to determine theexistence and location of any of the registration marks 21A and 21Bassociated with each of registration regions 47A and 47B. If none oronly part of these registration marks 21 are located, motion systems 59positions imaging head 26A to a next sub-scan position and anothercolumn of images is dynamically captured and analyzed. This process isrepeated until all of the registration features 21A and 21Bcorresponding to registration regions 47A and 47C are located.

Using the derived positional information for the first two registrationfeatures 21A and 21B, the location of the remaining registration feature21C for each registration region 47A and 47C is determined. Using theregistration region information 62 (which includes spacing informationbetween the various registration features) and the determined locationsof registration features 21A and 21B, controller 60 enables motionsystem 59 to move imaging head 26A to an estimated location in which theremaining registration feature 21C is placed in the center of a CCDcamera's field of view with no hunting. The objective of this process isto capture images of the remaining registration features 21C as quicklyas possible. In this regard the system will try to capture the remainingregistration features 21C of each of registration regions 47A and 47C ina single pass of CCD camera 50 using dynamic capture. Images ofregistration features 21C can be captured by moving imaging head 26A andits corresponding vision system 56 to the estimated location or movinganother vision system to the estimated location.

It is beneficial to determine the location of all the registration marksas quickly as possible. In this example embodiment of the invention, thelocation of the registration marks 21 corresponding to the registrationregions 47B and 47D are determined by the vision systems 56 associatedwith imaging head 26B while the registration marks 21 corresponding tothe registration regions 47A and 47C are being located.

In this example embodiment of the invention, the determined position ofeach set of the registration features 21 in turn determines the locationand position of their corresponding registration regions 47. In otherexample embodiments of the invention, the location and orientation ofeach registration region can be determined by other methods. Forexample, the vision systems 56 can be used to determine the location andorientation of a matrix 20 within each registration region 47.Determining the location and orientation of a matrix 20 can includedetermining the location and orientations of portions of the matrix 20.Portions of the matrix 20 can include edges and/or corners of the matrix20.

Step 310 includes an optional calibration routine (step 310 shown inbroken lines) for apparatus 50. For example, the position of the imagingbeams emitted by each of the imaging heads 26 are typically affected bychanges in temperature both inside and outside of the imaging heads 26.As the temperatures of various components change over time, the directedimaging beams can wander. This effect is called “thermal drift”.Calibration step 310 can adjust for thermal drift.

The location and orientation of each registration region 47 wasdetermined in step 320 with the use of the vision systems 50. In thisexample embodiment of the invention, this step in turn defined theposition and orientation of each matrix 20. The visual quality of theresulting color filers is dependant on the accurate transfer of imageforming material from a donor element 24 to specific areas defined bythe various cells 34. To determined how to move each of the imagingheads 26 so that they can accurately image the specific areas, thepositional relationship between the imaging beams and the field of viewthe CCD cameras 57 must be determined for each imaging head 26. Thoseskilled in the related art will realize that thermal drift can alterthese positional relationships. In this example embodiment of theinvention, these positional relationships are determined based on areference frame related to main-scan direction 44 and sub-scan direction42.

In an example embodiment of the invention, the positional relationshipis determined using beam finders 64. FIG. 6 schematically shows apartial cross-sectional view of apparatus 50. In this example embodimentof the invention a plurality of beam finders 64 (i.e. beam finder 64Aand beam finder 64 B). Although a single beam finder 64 can be used, aplurality of beam finders 64 allow for the calibration of a multiplicityof imaging heads 26 in a time efficient manner. Beam finders 64A and 64Bare located under carrier 51 which is used to support receiver element18A (not shown).

FIG. 7 shows beam finder 64 as per an example embodiment of theinvention. Beam finder 64 includes a mask 66 that defines areas thatinclude a sub-scan positional target 68, a camera target 69 and amain-scan positional target 70. Mask 66 can be produced byphoto-lithographic techniques. In this example embodiment of theinvention, sub-scan positional target 68 includes one or more regions 71(one in this example) that are aligned transversely to sub-scandirection 44 and main-scan positional target 70 includes one or moreregions 72 (i.e. one in this example) that are aligned at apredetermined angle to sub-scan direction 44. Photodiodes (not shown)are positioned in the vicinity of regions 71 and 72 and are responsiveto emit various signals when imaged by radiation. Camera target 69includes one or more regions 73 (one in this example). Light sources(not shown) are positioned in the vicinity of regions 73. Controller 60is operable for activating the light sources to illuminate to illuminateregion 73. The positions of sub-scan positional target 68, a cameratarget 69 and a main-scan positional target 70 is accurately determinedwith respect to each other.

For each imaging head 26, the positional relationship between itsimaging beams and the field of view its associated CCD camera 57 isdetermined by establishing relative movement between the imaging head 26and carrier 51 in the vicinity of a beam finder 64. Referring to FIGS. 6and 7, each imaging head 26 is moved along a respective path 76A or 76Baligned with sub-scan direction 44 while imaging associated beam finders64 with one or more imaging beams (not shown). As the one or moreimaging beams are moved across each beam finder, the photodiodes locatedin the vicinity of sub-scan positional target 68 and main-scanpositional target 70 are sampled. As the one or more imaging beams aremoved across sub-scan positional target 68, signals from the sampledphotodiodes will have intensity levels defined by a first peak 74 thatcorresponds to a sub-scan position of the one or more beams. As the oneor more imaging beams are moved across main-scan positional target 70,signals from the sampled photodiodes will have intensity levels definedby a second peak 75 that corresponds to a main-scan position of the oneor more beams. An example of first peak 74 and second peak 75 are shownschematically in FIG. 8.

FIG. 8 schematically shows a first peak 74 that includes an intensityplateau 77. The start and end of the intensity plateau are defined bysub-scan points 78 and 79 respectively. Sub-scan point 78 corresponds toa sub-scan position of the imaging head 26 in which all of the radiationemitted by its one or more imaging beams is first captured by thephotodiodes associated with sub-scan positional target 68. Sub-scanpoint 79 corresponds to sub-scan position of the imaging head 26 inwhich all of the radiation emitted by its one or more imaging beams islast captured by the photodiodes associated with sub-scan positionaltarget 68. Signals provided by sub-scan encoders of motion system 59 areused by controller 60 to thereby accurately determine the sub-scanposition of the one or more imaging beams.

FIG. 8 schematically shows a second peak 75 that includes an intensityplateau 80. The start and end of the intensity plateau are defined bysub-scan points 81 and 82 respectively. Sub-scan point 81 corresponds toa sub-scan position of the imaging head 26 in which all of the radiationemitted by its one or more imaging beams is first captured by thephotodiodes associated with main-scan positional target 70. Sub-scanpoint 82 corresponds to a sub-scan position of the imaging head 26 inwhich all of the radiation emitted by its one or more imaging beams islast captured by the photodiodes associated with main-scan positionaltarget 70. Controller 60 analyses signals provided by sub-scan encodersof motion system 59 representative of these sub-scan positions anddetermines a distance 83 between the first and second peaks 74 and 80.Distance 83 varies as a function of the main-scan position in which theone or more imaging beams crossed the main-scan positional target 70. Bycomparing the distance 83 with the varying spacing between rectangularshaped region 71 and parallelogram shaped region 72, controller 60 canthereby determine the main-scan position of the one or more imagingbeams.

After the sub-scan and main-scan positions of the one or more imagingbeams have been determined, controller 60 illuminates camera target 69.CCD camera 57 and microscope 61 are used to locate camera target 69 andsignals provided by sub-scan and main-scan encoders of motion system 59are used by controller 60 to thereby accurately determine the positionof CCD camera 57 at this location. Controller 60 can then establishpositional relationships between the imaging beams and CCD camera ofeach imaging head 26.

The mechanical alignment of various additional components in apparatus50 is not perfect. For example, support structures may not be perfectlytrue, and position encoders are not perfectly accurate. To compensatefor these and other imperfections, calibration step 310 can account forthem. The imperfections can be measured and a device correction mapincluding a two dimensional matrix of offsets from measured location toa true location can be determined for each imaging head 26.

Referring back to FIG. 5, step 330 prepares apparatus 50 for imaging.The location and orientation of each of the registration regions 47 hasbeen determined in step 320. In step 330 one or more “placementcorrection maps” are generated by controller 60 for each imaging head26. The placement correction maps are similar to the device correctionmaps except that they compensate for the placement of receiver element18A placement within template 52 and any skew associated withregistration regions 47 instead of device inaccuracies. Controller 60 isused to combine the device correction maps and the placement correctionmaps to create a final set of correction map for each imaging head 26.

Each set of final correction map covers the entire two dimensionalrelative range of motion that each imaging head 26 will undergo. In anexample embodiment of the invention, the final set of correction mapsincludes a sub-scan correction map and a main-scan correction map. Thesub-scan correction map includes information that is communicated bycontroller 60 to motion system 59 to define a coordinated motion pathfor each imaging head 26. The main-scan correction map is sent to theimaging electronics 84 to set various timing delays for imaging beamsemitted by imaging heads 26.

FIG. 9A schematically shows a receiver element 18B that includes aregistration region 47E (shown in broken lines). Registration region 47Eis skewed (i.e. the amount of skew has been exaggerated for the sake ofclarity) with respect to both main-scan direction 42 and sub-scandirection 44. Multi-channel imaging head 26C (herein referred to asimaging head 26C) is movable along a path aligned with sub-scandirection 44 while receiver element 18B is movable along a path alignedwith main-scan direction 42. In this case, it is desired that an image200 be formed on receiver element 18B in register with registrationregion 47E (registration region 47E being shown as larger than image 200for the sake of clarity). In this case, image 200 is in register withregistration region 47E when its edges are parallel to correspondingedges of registration region 47E.

FIG. 9B shows a conventional imaging of receiver element 18B. In thiscase imaging head 26C images receiver element 18B by generating aplurality of image swaths 202. Image information data 218 representingimage 200 is provided by controller 60 to imaging head 26C. Each swathis formed during a scan of imaging head 26C. In this case each swath 202is formed by scanning receiver element 18B along a path aligned withmain-scan direction 42, while maintaining imaging head 26C at a fixedsub-scan position. A movement of imaging head 26C along a path alignedwith sub-scan direction 44 is made between successively imaged swaths202. During each scan a portion of an image corresponding to an imagedswath 202 is formed on receiver element 18B. This imaging method howeverresults in the formation of image 200A that is not in register withregistration region 47E; a result which can diminish the visual qualityof the imaged receiver element 18B.

FIGS. 9C to 9D show a sequence of steps as per an example embodiment ofthe invention used to form an image in substantial registration withregistration region 47E. Referring to FIG. 9C, imaging head 26C andreceiver element 18B are moved in a synchronous fashion during eachscan. In this example embodiment of the invention, sub-scan motion iscoordinated with main-scan motion in accordance with the previouslyaforementioned correction maps. Controller 60 uses the correction mapsto achieve this coordinated motion by controlling motion system 59 (notshown) such that the sub-scan axis servo's target position is directlytied in real time to the correction map. As main-scan motion isestablished, the required synchronous sub-scan motion is defined by thecorrection maps and oriented swaths 202A. Employing coordinated motionduring the scans results in the formation of image 200B. Image 200B isformed with edges 204 and 206 that are in register with portions ofregistration region 47E. Coordinated motion can be used to form edges204 and 206 that are continuous and smooth, which can facilitate anaccurate registration of portion of a formed image with a portion of aregistration region.

FIG. 9C shows that while coordinated motion has resulted in theformation of image 200B with edges 204 and 206, edges 208 and 210 ofimage 200B are still not in register with registration region 47E. FIG.9D shows a step in which the activation timing for various channels inimaging head 26C are altered to produce an imaged region 200C that is inregister with registration region 47E and that is substantially close incharacteristics desired image 200. A channel is activated to emit or notemit imaging beams on the basis of image data. However, the actual timein which a channel can be activated to emit or not emit imaging beamscan be advanced or delayed by adjusting the activation timing of thechannel. Varying activation timing can be used to vary the position of aplurality of imaged areas with respect to one another. Varyingactivation timing can be used to vary the position of imaged andnon-imaged areas with respect to one another.

Image 200B (shown in broken lines) is shown in FIG. 9D as a referencefor the activation timing changes. In this example embodiment of theinvention, the activation timing (schematically represented by arrows312) is varied, thus forming image 200C with edges 214 and 216 that aresubstantially in register with registration region 47E. Edges 214 and216 are saw-tooth in nature but are aligned with corresponding portionsof registration region 47E. In some example embodiments of theinvention, the step sizes in the saw-tooth edge profiles are related tothe amount of activation timing delay associated with the imaging ofcorresponding areas. In other example embodiments of the invention, theimaging channel activation timing can be advanced. Controller 60 andimaging electronics 84 (not shown in FIG. 9) alter that activationtiming of various imaging channels in accordance with the calibrationmaps. The activation timing of all or a portion of the imaging channelsused during the imaging of each swath can be altered. In this exampleembodiment of the invention, all of the channels employed to image eachswath are given a uniform delay from swath to swath.

In other example embodiments of the invention, the image informationdata is modified to produce and imaged region that is in register withregistration region 47E and that is substantially close incharacteristics to desired image 200. As schematically shown in FIG. 9E,image information data 218 is modified in a process called “imageshearing” to produce a sheared image data 220. Sheared image data 220includes a modified raster file in which when imaged by imaged imaginghead 26C forms an image 200D with edges 222 and 224 that aresubstantially in register with registration region 47E. Edges 222 and224 are saw-tooth in nature. Unlike embodiments of the invention inwhich the activation timing changes dictate the rise heights of eachsaw-tooth, the rise 225 of each of saw-tooth steps in this embodimentare related to the size of the pixel 223 imaged by imaging head 26C inresponse to the modified data file.

FIGS. 9C and 9D show steps that employ coordinated motions and channelactivation timing changes to form an image in substantial registrationwith a registration region. FIGS. 9B and 9E show steps that employcoordinated motion and sheared images to form an image in substantialregistration with a registration region. Referring back to FIG. 4, aplurality of registration regions 47 are shown, several of which have adifferent orientation from one another. In this example embodiment ofthe invention, each registration region 47 is represented in thesub-scan and main-scan correction maps corresponding to the imagingheads 26 that are to image these respective registration regions. Thedetermined orientation and placement coordinates of each set ofregistration marks 21 in combination with the nominal registrationregion coordinates as defined in registration information 62 in turndefines the rotation, scale and shift for that particular registrationregion 47.

In an example embodiment of the invention corresponding to FIG. 4,different coordinated motions and imaging channel activation sequencesare employed for each of the imaging heads 26 to form images insubstantial registration with corresponding registration regions 47. Forexample, since registration region 47A is skewed by angle θ₁ andregistration region 47B is skewed by a different angle θ₂, imaging head26A will form an image in registration with registration region 47A witha different set of coordinated motion parameters and channel timingactivations than the set employed by imaging head 26B during theformation of an image in registration with registration region 47B. Inthis example embodiment of the invention, each imaging head 26A and 26Bcan have a different speed along the sub-scan direction while eachimaging head is imaging. In other example embodiments of the invention,different multi-channel imaging heads can have different speeds alongthe main-scan direction while each head is imaging. In other exampleembodiments of the invention, different multi-channel imaging heads canhave different speeds along the main-scan and sub-scan directions whileeach imaging head is imaging.

In an example embodiment of the invention, the activation timing ofvarious channels in each imaging head 26A and 26B will be occur atdifferent times while each imaging head is imaging. In other exampleembodiments of the invention, the activation timing of different numbersof channels is different for each imaging head 26A and 26B. In otherexample embodiments of the invention, the activation timing of differentgroups of channels is different for each imaging head 26A and 26B. Inother example embodiments of the invention, the activation timing ofvarious channels in imaging head 26A can be delayed while the activationtiming of various channels in imaging head 26B can be advanced.

Referring back to FIG. 4, imaging head 26A is also required to form animage in register with registration region 47C while also scanning overregistration region 47A. In this example embodiment of the invention,registration region 47C does not assume a skewed orientation but isshifted in the sub-scan direction 44 by distance Δ₁. Although imaginghead 26A need not undergo coordinated motion to form an image inregister with registration region 47C, imaging head 26A can undergocoordinated motion in the region between registration regions 47A and47C. The use of coordinated motion between successively formed imagescan allow an imaging head to be properly positioned during the imagingof the successive image. In other example embodiments of the invention,a plurality of images is formed during a scan of a multi-channel imaginghead over a receiver element. Each of the images are aligned differentlyfrom one another and the imaging head employs different coordinatedmotions and imaging channel activation sequences while imaging eachimage along the scan path. In other example embodiments of theinvention, a plurality of images is formed in registration with acorresponding plurality of registration regions during a scan of amulti-channel imaging head over a receiver element. Each of theregistration regions are aligned differently from one another and theimaging head employs different coordinated motions and imaging channelactivation sequences while imaging each image in registration with itscorresponding registration region.

When independent coordinated motions and imaging channel activationsequences are employed by each imaging head of an imaging system thatcomprises a plurality of imaging heads, each imaging head can be used toform corresponding images that are aligned differently from one another.These corresponding images can be formed on one or more receiverelements. When different coordinated motions and imaging channel timingsequences are employed by each imaging head of an imaging system thatcomprises a plurality of imaging heads, each imaging head can be used toform corresponding images that are substantially registered withregistration regions that have different orientations to one another.Multi-imaging head systems that employ independent coordinated motionsand imaging channel activation sequences can advantageously increaseproductivity.

In some example embodiments of the invention, the activation timing forvarious channels in a multi-channel imaging head are altered to alignvarious portions of an image with corresponding portions of aregistration region. One method of varying the activation timinginvolves adjusting the activation timing of imaging channels used toimage the features on a swath by swath basis. That is, a single uniformadjustment is made to the activation timing of all the active imagingchannels employed in any given swath. In other swaths, another singleuniform adjustment is made to the activation timing of all of the activeimaging channels employed in each of those swaths. In this manner, thisform of skew correction typically results in a saw-tooth correction inwhich the correction are made in terms of integer number of swaths.

In an another example embodiment of the invention corresponding to FIG.4, different coordinated motions and sheared image data 220 are employedfor each of the imaging heads 26 to form images in substantialregistration with corresponding registration regions 47. Sinceregistration region 47A is skewed by angle θ₁ and registration region47B is skewed by a different angle θ₂, imaging head 26A will form animage in registration with registration region 47A with a different setof coordinated motion parameters and sheared image data than the setemployed by imaging head 26B during the formation of an image inregistration with registration region 47B. In this example embodiment ofthe invention, each imaging head 26A and 26B has a different speed alongthe sub-scan direction while each imaging head is imaging. In otherexample embodiments of the invention, different multi-channel imagingheads can have different speeds along the main-scan direction while eachhead is imaging. In other example embodiments of the invention,different multi-channel imaging heads can have different speeds alongthe main-scan and sub-scan directions while each imaging head isimaging.

For some demanding applications (e.g. laser-induced imaging of colorfilters), swath by swath activation timing adjustments or sheared imagedata may not result in the formation of a repeating pattern of featuresthat is in substantial alignment with a repeating pattern ofregistration sub-regions. In applications like color filters, the visualquality of the final product is dependant upon the accuracy with which arepeating pattern of features (e.g. the pattern of color filterelements) is registered with a repeating pattern of registrationsub-regions (e.g. matrix). As the feature sizes are reduced this becomesincreasingly difficult to do especially when repeating patterns offeatures are formed. Registration further become complicated whenrepeating patterns of island features are imaged since registrationalong both the sub-scan direction 44 and main-scan direction 42 istypically required. Registration can also be adversely impacted as theimage swaths increase in size as the number of imaging channels inmulti-channel imaging head is increased to improve productivitythroughput.

FIG. 10A shows an orientation between two color features 226 and 228 anda matrix portion 230. Each of the color features 226 and 228 are islandfeatures which are to be imaged by imaging head 26D such that they areregistered with matrix 20. Imaging head 26D includes and array 227A ofindividually addressable channels 40. Imaging head 26D can include onedimensional or two dimensional arrays 227A of channels 40. In thisillustrated case, imaging head 26D includes a one dimensional array 227Awhose axis 231 is aligned with sub-scan direction 44. Imaging head 26Dimages each of the color features during a scan over receiver element18C. It is to be understood color features 226 and 228 can beconcurrently imaged during a given scan or separately imaged in separatescans. In this case it is required that color features 226 and 228overlap matrix 230 without overlapping each other. In this exampleembodiment of the invention, each of color features 226 and 228 areimaged by a plurality of imaging channels 40. In this example embodimentof the invention, each of color features 226 and 228 are imaged by aplurality of contiguous imaging channels 40.

Various factors must be considered when imaging color features 226 and228 such that they align matrix portion 230 without overlapping eachother. For example, each of the color features 226 and 228 must beimaged such that they overlap matrix portion 230 by a certain amount toachieve a desired quality characteristic of the color filter. A minimumrequired overlap for imaging each of the color features 226 and 228 canbe estimated from the following equation:Minimum Required Overlap (MRO)=Plotter Accuracy+MatrixRepeatability+Absolute Minimum Overlap, where:  (1)

Plotter Accuracy represents the accuracy of the imaging system used toimage color features 226 and 228. This accuracy can be affected by themechanical repeatability associated with the positioning of imaging head26D during the image, the beam finder accuracy, imaging beam drift; andthe roughness of the edges of the images that are formed. A typicalvalue for Plotter Accuracy can be in the range of +/−2.5 microns.

Matrix Repeatability represents the variation in the location of thematrix portion with respect to receiver element 18. A typical value forMatrix Repeatability is +/−0.5 microns.

Absolute Minimum Overlap represents the absolute minimum overlap that acolor feature is required to have to achieve a desired qualitycharacteristic. A typical value for Absolute Minimum Overlap is 1micron.

A Minimum Required Overlap (MRO) based on the above typical values canbe estimated to be approximately 4 microns.

Other factors can include the minimum gap requirement between the twocolor features 226 and 228 so that they do not overlap each other. Theminimum gap requirement can be affected by the imaging repeatabilityespecially when each of the color features 226 and 228 are imaged duringseparate scans. A minimum gap requirement can be estimated by thefollowing equation:Minimum Gap (MG)=2×Imaging Repeatability, where:  (2)

Imaging Repeatability represents the repeatability of positioning colorelements 226 and 228 in their intended positions. Imaging Repeatabilitycan be affected by the mechanical repeatability associated with thepositioning of imaging head 26D during the imaging, beam drift and theroughness of the edges of the images that are formed. A typical valuefor Imaging Repeatability is +/−2.5 microns to provide a Minimum Gap(MG) of 5 microns.

Other factors can include the addressability of imaging head 26D. Theability to control the size of each of the imaged color features 226 and228 is a function of the pixel size. For example, changing a size ofeach of the color features 226 and 228 by one pixel effectively meansthat the position of an edge of each feature changes by one half pixelwith respect to corresponding edge of matrix portion 230. A half pixelof margin between the Minimum Gap (MG) and the Minimum Required Overlap(MRO) is required to ensure that both these requirements can be met. Anaddressability requirement can be estimated from the following equation:Addressability=Matrix Line Width−2×Minimum Required Overlap(MRO)−Minimum Gap (MG), where:  (3)

Addressability refers to a pixel size characteristic as imaged by theimaging head 26D. In this particular case, addressability refers to apixel size characteristic in a main scan direction (i.e. main-scanaddressability). Main-scan addressability can be varied by adjusting theexposure timing of imaging channels 40 as they direct imaging beams.Varying the length of time that a given imaging beam interacts with amedia changes a rate in which the media is exposed which results in achange in the size of the pixel along a scanning direction. In thiscase, the exposure timing of channels 40 can be adjusted relative to themain-scan encoder associated with motion system 59. A digitallysynthesized phase lock loop can be used to control the imaging timingusing the main-scan encoder. Adjusting parameters in the loop can giveprecise control of the main-scan addressability and be used to vary asize of the imaged pixels along a scan direction. In various exampleembodiments of the invention, the size of the pixels along a scandirection is adjusted for various reasons. For example, it is preferredto image an integer number of pixels along a scan direction in each cell34 of the matrix 20 to ensure a consistent positioning of colorant ineach cell. Any systematic change in position could create imageartifacts such as banding. The size of the pixels can be adjusted toform a pattern of features in substantially alignment with a pattern ofregistration sub-region. It is preferred that the various features besized appropriately along the scan direction to each evenly overlapmatrix portions 230 to facilitate the MRO and MG requirements. It ispreferred that the various features be sized appropriately along thescan direction such that the pitch of the pattern of features matchesthe pitch of matrix cells 34 along the scan direction. In variousexample embodiments of the invention, the size of pixels along the scandirection is varied by varying the main-scan resolution. In applicationssuch as color filters, a main-scan addressability of approximately 5microns or smaller is desirable. In some example embodiments of theinvention, main-scan addressabilities are adjusted in accordance with apattern of registration sub-regions. In some example embodiments of theinvention, main-scan addressabilities are adjusted to have non-integervalues.

Matrix Line Width is size characteristic of matrix portion 230. In thisexample this is corresponds to a size W of matrix portion 230.

One may arrange equations (1), (2) and (3) and estimate a minimum matrixline width as follows:Matrix Line Width (W)=Addressability+2×Minimum Overlap+Minimum Gap.  (4)

By using the typical values discussed above, a minimum Matrix Line Width(W) can be estimated to be 18 microns (i.e. 5 microns+(2×4 microns)+5microns). Some conventional color filters have matrix line widths in theorder of 20 to 24 microns. It is desired to produce color filters withmatrix line width that are smaller than these conventional values.

FIG. 10A shows a desired case in which imaging head 26D is positionedwith respect to matrix 20 such that color features 226 and 228 areimaged with edges 232 and 234 that are aligned with axis 231 of channelarray of 227A. Edges 232 and 234 do not overlap each other and areformed in registration with matrix portion 230.

FIG. 10B shows a case in which matrix 20 is rotated by an angle θ₃ withrespect to axis 231 of channel array 227A of imaging head 26D. Colorfeatures such as color features 226 form part of a pattern that is to beformed in with matrix 20. In this case, the plurality of color features226 and color features 228 is imaged using coordinated motion techniquesduring each scan of imaging head 27D. An imaged swath 234A is producedduring a first scan and an image swath 234B is produced during a secondscan. In this case, each swath is imaged by an array of approximately900 imaging channels (exact number not shown), with an addressability of5 microns to produce a swath that is approximately 4.5 mm wide. Each ofthe color features 226 and 228 is imaged by 20 imaging channels and isregularly arranged in a pattern such that rows of fifteen color features226 (shown as color features 226(A) through 226(O) are formed duringeach scan. Color features 228 are arranged and imaged in a similarfashion (shown as color features 228(A) through 228(O)). Color features228 comprise different colors than color features 226 and are typicallyimaged in different scans than color features 226. For the sake ofclarity, not all of the color features 226(A) to 226(O) and 228(A) to228(O) and the matrix cells 34 are shown. In this case, each of thecolor features 226 and 228 repeat with a pitch corresponding to threecells 34.

In this case, matrix 20 is rotated with respect to imaging head 26D byangle θ₃ that is 1 milli-radian corresponding to a typical positionalvariation of receiver element 18C within the imaging system (FIGS. 10B,10C, 10D and 10E show exaggerated angles θ₃ for the sake of clarity). Tocompensate for this rotational error, the activation timing of all thechannels 40 used to produce each swath 234B is varied with respect tothe formation of swath 234A. An offset 229 equal to 4.5 microns isformed between the two imaged swaths 234A and 234B to compensate for the1 milli-radian rotation. Even such apparently minor offsets can howeverlead to numerous problems. For example, while the registration betweenmatrix 20 and the imaged color features 226(A) and 228(A) is notsignificantly affected by the swath-to-swath activation timing changes,the registration between matrix 20 and color features such colorfeatures 226(O) and 228(O) can be affected by the resulting offset.

FIGS. 10C and 10D schematically show possible registration affectsassociated with features such as color features 226(O) and 228(O). InFIG. 10C, case, the swath-to-swath activation timing has been delayedsuch that the Minimum Required Overlap is still substantially maintainedin each of color features 226(O) and 228(O). However, unlike colorfeatures 226(A) and 228(A), swath-to-swath activation timing changeshave caused imaged features 226(O) and 228(O) to be displaced by anamount substantially equal to the entire offset of 4.5 microns. Portions236 and 238 of the color features 226(O) and 228(O) impinge in theMinimum Gap region and increased the chances that they will overlap oneanother in an undesired condition (color features 226(O) and 228(O) areshown overlapping one another in region 235). In this case, the width Wof matrix portion 230 was 18 microns; the Minimum Gap between thefeatures was 5 microns, and the Minimum Required Overlap was 4 microns.Again it is to be understood that angle θ₃ has been exaggerated for thesake of clarity and may not be identical to that shown in FIG. 10B.

One may try to avoid impinging in the Minimum Gap area by delaying theactivation timing of channels 40 such that the Minimum Gap is maintainedas shown in FIG. 10D. This however portions 236 and 238 to impinge inthe Minimum Required Overlap region and increases the chances thatun-imaged areas 240 can result between the matrix portion 230 and theimaged color features. Again it is to be understood that angle θ₃ hasbeen exaggerated for the sake of clarity and that in actuality, portions236 and 238 would comprise more of a rectangular shape than theillustrated wedge shape shown in FIGS. 10C and 10D. Clearly, asincreased throughput requirements demand imaging heads with even greaternumbers of imaging channels, misregistration between various colorfeatures and the matrix can increase as the swath widths increase.

FIG. 10E shows the imaging of patterns of features 226 and 228 onreceiver element 18C of FIG. 10B but imaged as per an example embodimentof the invention. Matrix 20 is again rotated by an angle θ₃ with respectto imaging head 26D. In this embodiment, matrix 20 is rotated by angleθ₃ with respect to axis 231 of the channel array 227A. In this exampleembodiment of the invention, portions of each color features 226 and 228are imaged using coordinated motion techniques during each scan ofimaging head 26D. In other example, embodiment of the invention,portions of color features 226 and 228 can be imaged by othertechniques. An imaged swath 234C is produced during a first scan and animage swath 234D is produced during a second scan. Each color feature226 and 228 is imaged by 20 imaging channels 40. Each of the colorfeatures 226 and 228 are regularly arranged in a pattern that includesseveral rows of fifteen color features 226 (shown as color features226(A) through 226(O)) and several rows of color features 228 (shown ascolor features 228(A) through 228(O)). In this example embodiment of theinvention, each pattern of color features 226 and 228 is imaged during ascan of imaging head 26E. Color features 228 comprise different colorsthan color features 226 and are typically imaged in different scans thancolor features 226. Again, not all of the color features 226(A) through226(O) and color features 228(A) through 228(O) are shown for the sakeof clarity.

Matrix 20 is rotated with respect to imaging head 26D by angle θ₃ thatis again 1 milli-radian (θ₃ is exaggerated for the sake of clarity). Tocompensate for this rotational error and maintain a desired registrationbetween the matrix 20 and each of the color features 226 and 228, theactivation timing of various sub-groups 241 of channels in the array ofchannels is varied. In this example embodiment of the invention, channelsub-groups 241 each consist of 20 imaging channels. In other exampleembodiments of the invention, channels sub-groups 241 can consist of adifferent number of imaging channels 40. Since the 1 milli-radianrotation requires a total compensation of 4.5 microns across the entireswath, each channel sub-group 241 compensates for portion equivalent tothe number of channels in the channel sub-group 241. In this exampleembodiment of the activation timing of each of the subgroups of channelsis adjusted such that each of the corresponding portions of an imagedswath are offset from each other by an offset 247 equal to (20/900)×4.5microns or 0.1 microns. The offsets 247 are aligned with a scandirection associated with the imaging. In this example embodiment of theinvention, the scan direction is related to the coordinated motiontechniques employed. In other example embodiments of the invention, thescan direction can be aligned with main-scan direction 42. Variouschannels within various channel sub-groups 241 are activated to formimaged areas. Various channels within various channel sub-groups areactivated to form un-imaged areas. In this example embodiment of theinvention, since each of the color features are imaged by channelsub-groups 241 during a given scan, the color features themselves willbe offset from one another by an amount equal to multiples of 0.1microns. In this manner, each of the color features 226(A) through226(O) and color features 228(A) through 228(O) will each not bemis-registered with matrix 20 by more than 0.1 microns. This smalloffset amount will not impact the constraints imposed by the MinimumRequired Overlap and Minimum Gap requirements previously defined eventhough matrix 20 is rotationally skewed with respect to imaging head26D. Advantageously this facilitates the imaging of receiver elementsthat comprise matrixes with thinner lines.

Adjusting the activation timing of channel sub-groups 241 to produceoffsets as low as 0.1 microns is readily achieved without compromisingthe productivity of the imaging system. For example, for scanning speedsof up to 2 meters per second, and a 0.1 micron offset would correspondto a activation timing delay of 50 nanoseconds, which is readilyachievable by current activation electronics. Activation timing delaysof 8 nanosecond resolution have been used by the present inventors. Forsome applications shearing image data in accordance with the overalldegree of rotational skew may not provide the degree of registrationrequired between the imaged color features and the matrix. Shearingimage data produces a bit map file in which each bit corresponds to animaged or un-imaged pixel. Accordingly, sheared image data can lead toimaged offsets based on the addressability of the imaging system. In theprevious example, an individual channel addressability of 5 microns wasused and a resulting offset based on this value would not provide therequired registration between the matrix 20 and imaged color features226 and 228. Adjusting the activation timing of various channels, allowsfor the formation of offsets that are smaller than a characteristic sizeof the image pixels.

A pattern of registration sub-regions includes various spatialarrangements of registration sub-regions. Adjacent registrationsub-regions repeat in one or more directions within a pattern ofregistration sub-regions. As used hereinbelow, when something isdescribed as being not parallel to a pattern of registrationsub-regions, it refers to being not parallel to a line defined by adirection in which adjacent registration sub-regions repeat within thepattern of registration sub-regions. Adjacent registration sub-regionscan repeat in one or more directions within the pattern of registrationsub-regions. As herein described, being not parallel to a pattern ofregistration sub-regions can include being not parallel to a line in adirection in which adjacent registration sub-regions repeat along a rowof the pattern of registration sub-regions. As herein described, beingnot parallel to a pattern of registration sub-regions can include beingnot parallel to a line in a direction in which the adjacent registrationsub-regions repeat along a column of the pattern of registrationsub-regions. In some example embodiments of the invention, the patternof registration sub-regions is not parallel to an axis of a channelarray (e.g. axis 231). In some example embodiments of the invention, thepattern of the registration sub-regions is not parallel to a scandirection of imaging beams directed by imaging head 26D onto receiverelement 18C. In some example embodiments of the invention, relativemotion is established between the imaging head 26D and receiver element18D along a first direction that is not parallel to a pattern ofregistration sub-regions. In some example embodiments of the invention,a plurality of imaging channels 40 is activated to form an imaging line(e.g. imaging line 243 in FIG. 12) that is not parallel to a pattern ofregistration sub-regions.

In some example embodiments of the invention members of a plurality offeatures are imaged during separate scans of imaging head 26D bycorresponding channel sub-groups. The plurality of features can beimaged in an interleaved fashion. For example, first and second featurescan be imaged during a first scan by activating channels within one ormore channel sub-groups while a third feature is imaged between thefirst and second color features during a second scan by activatingchannels within an additional channel sub-group. The activation timingof at least one member of these channel sub-groups is different than theactivation timing of another of another member of these channelsub-groups.

In some example embodiments of the invention, the activation timing ofthe various channel sub-groups is controlled independently of whether ornot various channels within those channel sub-groups are activated todirect imaging beams. In some example embodiments of the invention,channel sub-groups are selected to correspond to one or more channelswhich are activated to direct imaging beams. In some example embodimentsof the invention, a first channel sub-group is selected to correspond toone or more channels which are activated to direct imaging beams while asecond channel sub-group is selected to correspond to one or morechannels which are controlled not to direct imaging beams.

In some example embodiments of the invention, the activation timing isdifferent for each member of a plurality of channel sub-groups, whereinat least one of the channel sub-groups is made up of a different numberof channels than another member of the channel sub-groups. In someexample embodiments of the invention a different number of channels in afirst channel sub-group are activated to direct imaging beams than thenumber of channel that are activated to direct imaging beams in a secondchannel sub-group.

In some example embodiments if the invention, a first portion of afeature is imaged by activating various channels within a first channelsub-group while a second portion of the feature is imaged by activatinga various channels within a second channel sub-group, the activationtiming of the first channel sub-group being different than theactivation ting of the second channel sub-group. In some exampleembodiments if the invention, the first portion and second portions ofthe feature correspond to first and second portions of an edge of thefeature. The activation timing of the first and second channelsub-groups can be controlled to offset the first and second edgeportions from one another. In applications such as the laser inducedthermal transfer of color filter features, such offsets may not bereadily visible due to the small magnitudes of the offsets between theedge portions and the image forming material transfer characteristics ofthe laser induced thermal transfer process. It is to be understoodhowever that these edge portion are imaged in an offset manner.

The number of channels selected for each channel sub-group can bedependant on the imaging speed which is related to the switchingresolution of the channel sub-groups. The number of channels selectedfor each channel sub-group can be dependant on the degree of rotationrequired between the imaged pattern of features and array of imagingchannels. For example, various example embodiments of the inventionemploying channels sub-groups made up of a plurality of imaging channelscan be used to image color filter features onto a matrix that is rotatedon the order of 1 milli-radian with the array of imaging channels. Asthis rotation angle increase to larger magnitudes (e.g. 10 degrees)embodiments of the invention employing sub-groups made up of a singlepixel would be more appropriate.

Referring back to FIG. 5, step 340 involves a pitch and substraterotation correction. A registration region represents a required boundsfor the image that is formed with respect to that region. In some casesa registration region includes a repeating pattern of sub-regions (e.g.a matrix) with which an imaged repeating pattern of features must beregistered. FIG. 11A shows an example of a desired registration of arepeating pattern of features with a registration region 47F made up ofa repeating pattern of sub-regions. In this example, the registrationregion 47F includes a matrix 20 that is made up of a plurality of matrixcells 34. Various features are formed with respect matrix cellstypically in a number of steps. In this case, it is desired that redfeatures 12A, green features 14A and blue features 16A be formed onreceiver element 18D. It is desired that each of the red features 12A,green features 14A and blue features 16A overlap portions of matrix 20to avoid undesirable back lighting effects. Each of the red features12A, green features 14A and blue features 16A are to overlap portions ofmatrix 20 without overlapping themselves. Accordingly, in this example,it is desired that the pitch “P_(f)” of each respective repeatingpattern of red features 12A, green features 14A and blue features 16Aequal substantially the pitch “P_(r)” of the repeating pattern ofsub-regions (i.e. matrix cells 34).

FIG. 11B schematically shows the difficulties of imaging the receiverelement 18D shown in FIG. 11A with conventional imaging techniques. FIG.11B schematically shows a conventional imaging process that attempts toimage desired red features 12A in register with corresponding matrixcells 34. The green features 14A and blue features 16A have been omittedfor the sake of clarity. Imaging head 26E forms a repeating pattern ofred features 12B that correspond to the desired pattern of red features12A. Imaging head 26E is movable along a path aligned with sub-scan axis44 and that includes an array 227B of individually addressable channels40 capable of emitting imaging beams. Channel array 227B can include aone dimensional array or a two dimensional array. In this exemplarycase, imaging head 26E assumes a typical orientation wherein an axis 231of array 227B is substantially parallel to the pattern of matrix cells34. As shown in FIG. 11B, the channel array 227B has an addressabilitythat cannot image the repeating pattern of red features 12A with aninitial pitch “P_(i)” that is equal to the pitch P_(r) of the matrixcells 34 onto which the red features 12B are imaged onto. The ability tocontrol the size and position of each of the imaged red features 12B isa function of the pixel size. Imaging beams generated by imaging head26E each create a pixel of a size that cannot generated the desiredpattern of the red features 12A. The imaged red features 12B overlapcorresponding cells 34 by varying amounts. In this case, the amount ofcell overlap of some of the red features 12B has increased to a pointwhere those red features 12B would be overlapped by other featuresimaged with other donor elements which can result in various problemsincluding the aforementioned problems. In some cases where a number ofred features 12B are imaged in a given swath, some of these red features12B may fail to overlap a matrix line altogether and create undesiredun-imaged areas 242.

FIG. 11C schematically shows an imaging of the receiver element 18Dshown in FIG. 11A as per an example embodiment of the invention. FIG.11C shows only an imaging process related to desired red features 12A.The green features 14A and blue features 16A have been omitted for thesake of clarity. Patterns of green features 14A and blue features 16Acan be imaged as per this or other example embodiments of the invention.Red features 12C are imaged with the imaging head 26E which was used inthe conventional imaging techniques shown in FIG. 11B. In this exampleembodiment of the invention, imaging head 26E is rotated with respect tomatrix 20. In this embodiment, imaging head 26E is rotated by an angleθ₄ as measured from the sub-scan direction 44 to the axis 231 of thearray 227B. Angle θ₄ is selected so that the imaging swath produced byrotated imaging head 26E is sized to produce imaging beams that causethe pattern of red features 12C to be imaged with a pitch P_(f) that isequal to the pitch P_(r) of the matrix cells 34. In this exampleembodiment of the invention, the pitch distance between each of the redfeatures 12C is adjusted by the rotation of imaging head 26E to adjustthe spacing between the imaged red features 12C. Rotation of the imaginghead 26E also causes the size of the imaged pixels to change. In thisexample embodiment of the invention, the size of the pixels are changedin a direction generally perpendicular to an image swath formed byimaging head 26E. Changes in pixel size can be noted along sub-scandirection 42. Changes in pixel sizes can cause a size of the imaged redfeatures 12C to vary slightly from the targeted size of red features12A. Size deviations between each the imaged red features 12C andtargeted red features 12A are affected by the inherent sub-scanaddressability of the array of imaging channels 40. In this embodiment,to practice the invention, a sufficient number of channels is selectedto image each of the features with a sufficient number of adjusted pixelsizes. In applications such as color filter imaging, each of the colorfeatures will typically be allowed to overlap the matrixes within acertain range that can accommodate these variations. Rotation of thearray of imaging channels 40 by angle θ₄ with respect to matrix 20allows the pitch of the repeating pattern of red features 12C to matchthe pitch of the matrix cells 34 thus ensuring a consistent degree ofoverlap between all of the imaged red features 12C and the matrix 20.Embodiments of the invention can also be used to image repeatingpatterns of other features in similar fashions.

Although in the embodiment of the invention shown in FIG. 11C, imaginghead 26E was rotated from a initial position that was parallel tosub-scan direction 44, in other example embodiments of the invention,imaging head 26E is rotated by an appropriate angle from initialpositions that are not necessarily so.

FIG. 12 schematically shows the imaging of the receiver element 18D asper an example embodiment of the invention. Receiver element 18D isidentical to that shown in FIG. 11 with the exception that it is skewedby an angle ρ with respect to main-scan direction 42. FIG. 12 shows onlyan imaging process related to the imaging of red features 12A. Greenfeatures 14A and blue features 16A have been omitted for the sake ofclarity. The array 227B of individually addressable channels 40 inimaging head 26E are activated to direct imaging beams to form ascanning imaging line 243 used to form red features 12D. In this exampleembodiment of the invention, imaging head 26E is movable along a pathsubstantially parallel to sub-scan direction 44. Relative motion isestablished between imaging head 26E and receiver element 18B in adirection aligned with main-scan direction 42. The array 227B of imagingchannels 40 is controlled to emit the imaging beams while scanning alonga scan path. In this example embodiment of the invention, the channelarray is rotated with respect to matrix 20 to cause the pattern of redfeatures 12D to be imaged with an effective pitch P_(reff) that is equalto the effective pitch P_(reff) of the matrix cells 34. As shown in FIG.12, channel array 227B is rotated by angle θ₅, which in this embodimentis measured from the sub-scan direction 44 to the axis 231 of the array227B. The amount of required rotation of channel array 227B is dependanton the initial amount of skew between the matrix 20 and the channelarray 227B. The initial skew alters the inherent pitch P_(r) of thematrix cells to create an effective pitch P_(reff). In this exampleembodiment of the invention, the effective pitch P_(reff) is determinedalong a direction that is parallel to imaging line 243.

In this example embodiment of the invention matrix 20 is skewed. withThe repeating pattern of red features 12D is also imaged in a skewedmanner. Various example embodiments of the invention may image in askewed manner by controlling the imaging beams emitted by imaging head26E to image the edges of each feature with a stair-cased arrangement ofimaged pixels. Another method for imaging the skewed edges of thefeatures is to use coordinated motion. In some example embodiments ofthe invention, the channel array 227B is operable to direct imagingbeams along a scan path, and matrix 20 is skewed with respect to thescan path. This skew alters the inherent pitch P_(r) of the matrix cellsto create an effective pitch P_(reff) and a pattern of features isimaged with an effective pitch P_(reff) that is equal to the effectivepitch P_(reff). The pattern of features can be imaged by rotating thechannel array 227A to account for this skew. FIG. 13 schematically showsthe imaging of the receiver element 18D shown in FIG. 11 as per anotherexample embodiment of the invention. FIG. 13 shows only an imagingprocess related to the imaging of red features 12A. The green features14A and blue features 16A have been omitted for the sake of clarity. Redfeatures 12E are imaged with an imaging head 26F. In this exampleembodiment of the invention, imaging head 26F includes zoom mechanism250. Zoom mechanism 250 adjusts a size of the imaging beams emitted byimaging head 26F such that a pattern of red features 12E are imaged witha pitch P_(f) that is equal to the pitch P_(r) of the matrix cells 34onto which the red features 12E are imaged ontoZoom mechanism 250 canadjust a size of the imaging beams to adjust a size of pixels imaged bythese beams. In the case where the matrix is skewed with respect to ascan path of imaging head 26F, zoom mechanism 250 can be operated tocause the pattern of red features 12E to be imaged with an effectivepitch that is equal to the effective pitch P_(reff) of the matrix cells.

FIG. 14 schematically shows a zoom system 250 employed in an exampleembodiment of the invention. Zoom system 250 includes a fixed fieldoptical component 252, two or more moving zoom optical components 254,an aperture stop 256, a fixed field component 258, and a moving focusoptical component 260. In this example embodiment of the invention,aperture stop 256 is located between the moving zoom optical componentsand the fixed field optical components 252. Zoom mechanism 250 maintainsthe locations of the object plane 262 and image planes 264 through thezoom adjustment range. The location of the moving zoom opticalcomponents 254 are moved according to a schedule to set themagnification of the optical system. Each of the various opticalcomponents consist of one or more optical elements. One or more of theoptical elements may be anamorphic. Other example embodiments of theinvention can use other zoom mechanisms.

A pitch of the pattern of registration sub-regions (e.g. a matrix) canbe determined in various ways, including by direct measurement. Forexample, beam finders can be used to determine an inherent or effectivepitch of a pattern of registration sub-regions. Sizes of imaged pixels,imaging beams and/or an imaged swath can also be determined bymeasurement and can be used to help match the pitch of a repeatingpattern of features to the pitch of a repeating pattern of registrationsub-regions.

The size of pixels can be adjusted as per one or more exampleembodiments of the invention. In some example embodiments of theinvention the size of pixel in a first direction is changed differentlyfrom the size of a pixel in a second direction. The second direction canbe substantially perpendicular to the first direction. In some exampleembodiments of the invention, the size of a pixel in a sub-scandirection is changed differently from the size of a pixel in a main-scandirection. In some example embodiments of the invention the sizecharacteristic of the pixel is adjusted to have different sizes indifferent directions. In some example embodiments of the invention, acharacteristic of the pixel is adjusted in different directions by thedifferent methods. In some example embodiments of the invention the sizeof a pixel is adjusted in a first direction independently of the size ofthe pixel in a second direction. In some example embodiments of theinvention, the size of a pixel in a sub-scan direction is adjustedindependently of a size of the pixel in a main-scan direction.

Once the orientation of various registration regions is known, repeatingpatterns of features are imaged in register with the registrationregions as per step 350 in FIG. 5. Imaging can be accomplished indifferent manners. For example, referring to imaging apparatus 50 ofFIG. 4, imaging is performed by positioning each of the imaging heads26A and 26B along a sub-scan direction 44 to start positions retrievedfrom controller 60 as calculated from registration calculations.Receiver element 18A is positioned along main-scan direction 42 to startposition provided by controller 60. This start position takes intoaccount the distance required to accelerate to imaging speed. Apparatus50 then accelerates receiver element 18A to the imaging speed. Thismoves receiver element 18A to the correct position at the correctvelocity under imaging heads 26A and 26B. At the same time that receiverelement 18A is being moved, each of the imaging heads 26A and 26B ismoved along sub-scan direction 42 in a coordinated fashion. Imagingheads 26A and 26B are controlled to emit imaging beams towards receiverelement 18A to form various imaged swaths. If each of the imaging heads26A and 26B are imaging over different registration regions 47, thespeed and activation timing for each imaging head is independent of theothers. As imaging heads 26A and 26B complete their respective swaths,their main-scan motion is reversed and at the same time, the imagingheads 26 are moved a portion or all of a swath width along sub-scandirection 44. Imaging apparatus can image receiver element 18A in bothdirections of the main-scan motion. Other example embodiments of theinvention can include other imaging methods.

Imaging heads 26 may comprise any suitable multi-channel imaging headhaving individually-addressable channels 40, each channel capable ofproducing an imaging beam having an intensity or power that can becontrolled. Any suitable mechanism may be used to generate imagingbeams. The imaging beams may be arranged in any suitable way.

Some embodiments of the invention employ infrared lasers. Infrared diodelaser arrays employing 150 μm emitters with total power output of around50 W at a wavelength of 830 nm, have been successfully used in thepresent invention. Alternative lasers including visible light lasers mayalso be used in practicing the invention. The choice of laser sourceemployed may be motivated by the properties of the media to be imaged.

As shown in FIG. 4, data 63 representing feature patterns 30 is input tocontroller 60. Without limitation, a feature pattern 30 may represent apattern of color features forming a portion of a color filter.

Various example embodiments of the invention have been described interms of a laser induced thermal transfer processes in which an imageforming material is transferred to a receiving element. Other exampleembodiments of the invention can be employed with other imaging methodsand media. Images can be formed on media by different methods withoutdeparting from the scope of the present invention. For example, mediacan include an image modifiable surface, wherein a property orcharacteristic of the modifiable surface is changed when irradiated byan imaging beam to form an image. An imaging beam can be used to ablatea surface of media to form an image. Those skilled in the art willrealize that different imaging methods can be readily employed.

A program product 67 can be used by controller 60 to perform variousfunctions required by apparatus 50. One function includes settingcontrol parameters for imaging heads 26 to register one or morerepeating patterns of features 30 with one or more repeatingregistration patterns 36 of registration sub-regions. Withoutlimitation, program product 67 may comprise any medium which carries aset of computer-readable signals comprising instructions which, whenexecuted by a computer processor, cause the computer processor toexecute a method as described herein. The program product 67 may be inany of a wide variety of forms. The program product 67 may comprise, forexample, physical media such as magnetic storage media including floppydiskettes, hard disk drives, optical data storage media including CDROMs, DVDs, electronic data storage media including ROMs, flash RAM, orthe like. The instructions may optionally be compressed and/or encryptedon the medium.

For the methods described herein repeating patterns of features 30 canhave the form of stripes that have edges aligned with main scandirection 42. Repeating patterns of features 30 can also includerepeating patterns of island features. The invention is not limited toimaging rectangular shaped island features, however.

Features may be imaged in accordance with image data that includeshalftone screening data. In halftone imaging, features comprise apattern of elements known halftone dots. The halftone dots vary in sizeaccording to the desired lightness or darkness of the imaged feature.Each halftone dot is typically larger than pixels imaged by imaging headand is typically made up of a matrix of pixels imaged by a plurality ofimaging channels. Halftone dots are typically imaged at a chosen screenruling typically defined by the number of halftone dots per unit lengthand a chosen screen angle typically defined by an angle at which thehalftone dots are oriented. In example embodiments of the invention, afeature may be imaged with a screen density in accordance with thecorresponding halftone screen data chosen to image that feature.

In other example embodiments of the invention, a feature may be imagedwith stochastic screen made up of a varying spatial frequency of equallysized dots. In yet other example embodiments of the invention, a featuremay be imaged with a combined halftone and stochastic screen (commonlyreferred to as a “hybrid” screen).

Patterns of features have been described in terms of patterns of colorfeatures in a display. In some example embodiments of the invention, thefeatures can be part of an LCD display. In other example embodiments ofthe inventions, the features can be part of an organic light-emittingdiode (OLED) display. OLED displays can include differentconfigurations. For example, in a fashion similar to an LCD display,different color features can be formed into a color filter used inconjunction with a white OLED source. Alternatively, different colorillumination sources in the display can be formed with different OLEDmaterials with various embodiments of the invention. In theseembodiments, the OLED based illumination sources themselves control theemission of colored light without necessarily requiring a passive colorfilter. OLED materials can be transferred to suitable media. OLEDmaterials can be transferred to a receiver element with laser-inducedthermal transfer techniques.

While the invention has been described using as examples applications indisplay and electronic device fabrication, the methods described hereinare directly applicable to imaging any patterns of features includingthose used in biomedical imaging for lab-on-a-chip (LOC) fabrication.LOC devices may include several repeating patterns of features. Theinvention may have application to other technologies, such as medical,printing and electronic fabrication technologies.

It is to be understood that the exemplary embodiments are merelyillustrative of the present invention and that many variations of theabove-described embodiments can be devised by one skilled in the artwithout departing from the scope of the invention. It is thereforeintended that all such variations be included within the scope of thefollowing claims and their equivalent.

1. A method for forming a plurality of images on a media comprising: operating a first imaging head comprising a first plurality of individually addressable channels to direct imaging beams to form a first image on the media while scanning over the media along a first scan path; operating a second imaging head comprising a second plurality of individually addressable channels to direct imaging beams to form a second image on the media while scanning over the media along a second scan path; wherein the first scan path is not parallel to the second scan path, and the first image is not aligned with the second image; and further comprising establishing a first relative speed between the first imaging head and the media while the first imaging head is imaging the media, and establishing a second relative speed between the second imaging head and the media while the second imaging head is imaging the media, wherein the first relative speed is different from the second relative speed.
 2. A method according to claim 1, wherein the first image is skewed with respect to the second image.
 3. A method according to claim 1, comprising operating the first imaging head to image the media while operating the second imaging head to image the media.
 4. A method according to claim 1, comprising activating a portion of the first plurality of imaging channels to direct imaging beams while activating a portion of the second plurality of imaging channels to direct imaging beams.
 5. The method of claim 1, comprising operating the first imaging head to direct imaging beams to form a third image on the media while scanning over the media along a third scan path, wherein the third image is not aligned with the first image.
 6. A method according to claim 5, wherein the third image is skewed with respect to the first image.
 7. A method according to claim 5, wherein the third scan path is not parallel with the first scan path.
 8. A method according to claim 1, wherein the media comprises one or more registration regions, the method comprising aligning the first scan path to image a portion of the first image in substantial registration with a first registration region, by causing relative motion along both a main-scan direction and a sub-scan direction.
 9. A method according to claim 1, wherein forming the first image and forming the second image comprises imaging the first image and the second image in a laser-induced thermal transfer process.
 10. The method according to claim 9, wherein the laser-induced thermal transfer process comprises a laser-induced dye transfer process.
 11. A method according to claim 9, wherein the laser-induced thermal transfer process comprises a laser-induced mass transfer process.
 12. A method according to claim 9 wherein the media comprises one or more registration regions comprising a matrix produced from a method other than a laser-induced thermal transfer process.
 13. A method according to claim 1, wherein forming the first image and forming the second image comprises transferring an image forming material from a donor element to the media.
 14. A method according to claim 1, wherein forming the first image and forming the second image comprises transferring a colorant and a binder to the media.
 15. A method according to claim 1 wherein the first and second scan paths are straight.
 16. A method according to claim 1, wherein the media comprises a pattern of registration sub-regions, and the plurality of images comprises one or more patterns of features, the method comprising registering the one or more patterns of features with the pattern of registration sub-regions.
 17. A method according to claim 16, wherein the pattern of registration sub-regions comprises a matrix, and the one or more pattern of features comprises a pattern of color features.
 18. A method according to claim 17, wherein the pattern of color features forms a portion of a color filter.
 19. A method according to claim 17, wherein the pattern of color features forms a pattern of colored illumination sources.
 20. A method according to claim 19, wherein the colored illumination sources comprises an OLED material.
 21. A method for forming a plurality of images on a media comprising: operating a first imaging head comprising a first plurality of individually addressable channels to direct imaging beams to form a first image on the media while scanning over the media along a first scan path; operating a second imaging head comprising a second plurality of individually addressable channels to direct imaging beams to form a second image on the media while scanning over the media along a second scan path; wherein the first scan path is not parallel to the second scan path, and the first image is not aligned with the second image; and further comprising moving the first imaging head at a first speed while the first imaging head is imaging the media and moving the second imaging head at a second speed while the second imaging head is imaging the media, wherein the first speed is different from the second speed.
 22. A method for forming a plurality of images on a media comprising: operating a first imaging head comprising a first plurality of individually addressable channels to direct imaging beams to form a first image on the media while scanning over the media along a first scan path; operating a second imaging head comprising a second plurality of individually addressable channels to direct imaging beams to form a second image on the media while scanning over the media along a second scan path; wherein the first scan path is not parallel to the second scan path, and the first image is not aligned with the second image; and wherein channels of each of the first and second imaging heads are controlled by activation timing, the method comprising varying the activation timing of a portion of the channels of at least one of the first plurality of individually addressable channels and the second plurality of individually addressable channels.
 23. A method for forming a plurality of images on a media comprising: operating a first imaging head comprising a first plurality of individually addressable channels to direct imaging beams to form a first image on the media while scanning over the media along a first scan path; operating a second imaging head comprising a second plurality of individually addressable channels to direct imaging beams to form a second image on the media while scanning over the media along a second scan path; wherein the first scan path is not parallel to the second scan path, and the first image is not aligned with the second image; and wherein channels of each of the first and second imaging heads are controlled by activation timing, the method comprising varying the activation timing of each of the first plurality of individually addressable channels and the second plurality of individually addressable channels.
 24. A method for forming a plurality of images on a media comprising: operating a first imaging head comprising a first plurality of individually addressable channels to direct imaging beams to form a first image on the media while scanning over the media along a first scan path; operating a second imaging head comprising a second plurality of individually addressable channels to direct imaging beams to form a second image on the media while scanning over the media along a second scan path; wherein the first scan path is not parallel to the second scan path, and the first image is not aligned with the second image; and wherein channels of each of the first and second imaging heads are controlled by activation timing, the method comprising delaying the activation timing of a portion of the first plurality of individually addressable channels by a first period of time and delaying the activation timing of a portion of the second plurality of individually addressable channels by a second period of time, wherein the first period of time is different from the second period of time.
 25. A method for forming a plurality of images on a media comprising: operating a first imaging head comprising a first plurality of individually addressable channels to direct imaging beams to form a first image on the media while scanning over the media along a first scan path; operating a second imaging head comprising a second plurality of individually addressable channels to direct imaging beams to form a second image on the media while scanning over the media along a second scan path; wherein the first scan path is not parallel to the second scan path, and the first image is not aligned with the second image; and wherein channels of each of the first and second imaging heads are controlled by activation timing, the method comprising advancing the activation timing of a portion of the first plurality of individually addressable channels by a first period of time and advancing the activation timing of a portion of the second plurality of individually addressable channels by a second period of time, wherein the first period of time is different from the second period of time.
 26. A method for forming a plurality of images on a media comprising: operating a first imaging head comprising a first plurality of individually addressable channels to direct imaging beams to form a first image on the media while scanning over the media along a first scan path; operating a second imaging head comprising a second plurality of individually addressable channels to direct imaging beams to form a second image on the media while scanning over the media along a second scan path; wherein the first scan path is not parallel to the second scan path, and the first image is not aligned with the second image; and wherein channels of each of the first and second imaging heads are controlled by activation timing, the method comprising advancing the activation timing of a portion of the first plurality of individually addressable channels and delaying the activation timing of a portion of the second plurality of channels.
 27. A method for forming a plurality of images on a media comprising: operating a first imaging head comprising a first plurality of individually addressable channels to direct imaging beams to form a first image on the media while scanning over the media along a first scan path; operating a second imaging head comprising a second plurality of individually addressable channels to direct imaging beams to form a second image on the media while scanning over the media along a second scan path; wherein the first scan path is not parallel to the second scan path, and the first image is not aligned with the second image; and wherein channels of each of the first and second imaging heads are controlled by activation timing, the method comprising varying the activation timing of a first group of channels of the first plurality of individually addressable channels and varying the activation timing of a second group of channels of the second plurality of individually addressable channels, wherein the number of channels in the first group is different than the number of channels in the second group.
 28. A method for forming a plurality of images on a media comprising: operating a first imaging head comprising a first plurality of individually addressable channels to direct imaging beams to form a first image on the media while scanning over the media along a first scan path; operating a second imaging head comprising a second plurality of individually addressable channels to direct imaging beams to form a second image on the media while scanning over the media along a second scan path; wherein the first scan path is not parallel to the second scan path, and the first image is not aligned with the second image; wherein the media comprises one or more registration regions, the method comprising aligning the first scan path to form a portion of the first image in substantial registration with a first registration region; and further comprising aligning the second scan path to form a portion of the second image in substantial registration with a second registration region.
 29. A method for forming a plurality of images on a media comprising: operating a first imaging head comprising a first plurality of individually addressable channels to direct imaging beams to form a first image on the media while scanning over the media along a first scan path; operating a second imaging head comprising a second plurality of individually addressable channels to direct imaging beams to form a second image on the media while scanning over the media along a second scan path; wherein the first scan path is not parallel to the second scan path, and the first image is not aligned with the second image; wherein the media comprises one or more registration regions, the method comprising aligning the first scan path to form a portion of the first image in substantial registration with a first registration region; and wherein channels of each of the first and second imaging heads are controlled by activation timing, the method comprising varying the activation timing of a portion of the first plurality of individually addressable channels to form an additional portion of the first image in substantial registration with the first registration region.
 30. A method according to claim 29, wherein the first image comprises a repeating pattern of island features.
 31. A method according to claim 30, wherein the registration region comprises a repeating pattern of registration sub-regions, the method further comprising registering the repeating pattern of island features with the repeating pattern of registration sub-regions.
 32. A method according to claim 30 wherein the repeating pattern of island features comprises a first plurality of features of a first color, each feature of the first plurality of features separated from each other feature of the first color by a feature of a different color.
 33. A method according to claim 30 wherein the repeating pattern of island features comprises a first plurality of features of a first color, some features of the first plurality of features separated from some other feature of the first color by a feature of a different color in a first direction.
 34. A method according to claim 33 wherein the first direction is parallel to the first scan path.
 35. A method according to claim 30 wherein the repeating pattern of island features comprises a first plurality of features of a first color, some features of the first plurality of features separated from some other feature of the first color by a feature of a color other than the first color in a first direction and a second direction perpendicular to the first direction.
 36. A method for forming a plurality of images on a media comprising: operating a first imaging head comprising a first plurality of individually addressable channels to direct imaging beams to form a first image on the media while scanning over the media along a first scan path; operating a second imaging head comprising a second plurality of individually addressable channels to direct imaging beams to form a second image on the media while scanning over the media along a second scan path: wherein the first scan path is not parallel to the second scan path, and the first image is not aligned with the second image; wherein the media comprises one or more registration regions, the method comprising aligning the first scan path to form a portion of the first image in substantial registration with a first registration region; and further comprising activating the first plurality of imaging channels in accordance with image data provided to the first plurality of imaging channels, the method comprising modifying the image data to form an additional portion of the first image in substantial registration with the first registration region.
 37. A method according to claim 36, wherein modifying the image data comprises shearing the image data to match an orientation of the first registration region.
 38. A method for forming a plurality of images on a media comprising: operating a first imaging head comprising a first plurality of individually addressable channels to direct imaging beams to form a first image on the media while scanning over the media along a first scan path; operating a second imaging head comprising a second plurality of individually addressable channels to direct imaging beams to form a second image on the media while scanning over the media along a second scan path; wherein the first scan path is not parallel to the second scan path, and the first image is not aligned with the second image; wherein the media comprises one or more registration regions, the method comprising aligning the first scan path to form a portion of the first image in substantial registration with a first registration region; wherein the first image comprises a pattern of features, wherein the features are spatially separated from one another at least in a direction perpendicular to the first scan path; and wherein each feature of the pattern is screened with one of a half tone screen or a stochastic screen. 